Circular inserts for use in lathe tools and the like have been constructed with uniform chip control grooves provided in the outer periphery of the cutting face adjacent and sometimes extending to the cutting edge.
It is also known in the art to provide a succession of chip control recesses formed on the cutting face at the outer periphery along the cutting edge which are generally spherical and may intersect or contact each other as well as the cutting edge as shown in U.S. Pat. No. 4,273,480 or may intersect the cutting edge with space between the depressions as disclosed in U.S. Pat. No. 4,215,957. The latter patent also discloses alternative depressions which are generally rectangular with inner corners spaced from the cutting edge being rounded. Depressions such as disclosed in the latter patent are also believed to have been disposed around the periphery of circular inserts for use in lathe tools in a manner similar to the present invention.
In the aforementioned co-pending application, circular inserts are disclosed with overlapping depressions in the cutting face intersecting the cutting edge which are formed as arcuate segments of a conical form having a laterally extending cone axis intersecting the cutter axis. The depressions are preferably spaced at 30.degree. intervals and extend in a vertical direction to a depth providing approximately two-thirds overlap at the cutting edge perimeter. At each overlapping area a secondary conical depression form is provided with the axis of the cone bisecting the overlapping area in plan view. In preparing a master insert a conical grinder is employed having oppositely tapered intersecting conical surfaces adapted respectively to form the inner extremity of each depression at a relatively steep angle and the main portion of each depression at a relatively shallow angle relative to the cutting face.